From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0E51CCA9EC2 for ; Tue, 29 Oct 2019 08:11:07 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id CE6B320663 for ; Tue, 29 Oct 2019 08:11:06 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org CE6B320663 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 7FA8D6B0005; Tue, 29 Oct 2019 04:11:06 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 7AA946B0006; Tue, 29 Oct 2019 04:11:06 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 6BEED6B0007; Tue, 29 Oct 2019 04:11:06 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0067.hostedemail.com [216.40.44.67]) by kanga.kvack.org (Postfix) with ESMTP id 435166B0005 for ; Tue, 29 Oct 2019 04:11:06 -0400 (EDT) Received: from smtpin10.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with SMTP id 0CFD9181AEF1D for ; Tue, 29 Oct 2019 08:11:05 +0000 (UTC) X-FDA: 76096101690.10.kite06_60b5a011fa44d X-HE-Tag: kite06_60b5a011fa44d X-Filterd-Recvd-Size: 4948 Received: from mx1.suse.de (mx2.suse.de [195.135.220.15]) by imf26.hostedemail.com (Postfix) with ESMTP for ; Tue, 29 Oct 2019 08:11:04 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id DE898B69C; Tue, 29 Oct 2019 08:11:02 +0000 (UTC) Date: Tue, 29 Oct 2019 09:11:02 +0100 From: Michal Hocko To: zhong jiang Cc: akpm@linux-foundation.org, hannes@cmpxchg.org, ktkhai@virtuozzo.com, linux-mm@kvack.org, Minchan Kim Subject: Re: [PATCH] mm: fix unevictable page reclaim when calling madvise_pageout Message-ID: <20191029081102.GB31513@dhcp22.suse.cz> References: <1572275317-63910-1-git-send-email-zhongjiang@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1572275317-63910-1-git-send-email-zhongjiang@huawei.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: [Cc Minchan] On Mon 28-10-19 23:08:37, zhong jiang wrote: > Recently, I hit the following issue when running in the upstream. > > kernel BUG at mm/vmscan.c:1521! > invalid opcode: 0000 [#1] SMP KASAN PTI > CPU: 0 PID: 23385 Comm: syz-executor.6 Not tainted 5.4.0-rc4+ #1 > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1ubuntu1 04/01/2014 > RIP: 0010:shrink_page_list+0x12b6/0x3530 mm/vmscan.c:1521 > Code: de f5 ff ff e8 ab 79 eb ff 4c 89 f7 e8 43 33 0d 00 e9 cc f5 ff ff e8 99 79 eb ff 48 c7 c6 a0 34 2b a0 4c 89 f7 e8 1a 4d 05 00 <0f> 0b e8 83 79 eb ff 48 89 d8 48 c1 e8 03 42 80 3c 38 00 0f 85 74 > RSP: 0018:ffff88819a3df5a0 EFLAGS: 00010286 > RAX: 0000000000040000 RBX: ffffea00061c3980 RCX: ffffffff814fba36 > RDX: 00000000000056f7 RSI: ffffc9000c02c000 RDI: ffff8881f70268cc > RBP: ffff88819a3df898 R08: ffffed103ee05de0 R09: ffffed103ee05de0 > R10: 0000000000000001 R11: ffffed103ee05ddf R12: ffff88819a3df6f0 > R13: ffff88819a3df6f0 R14: ffffea00061c3980 R15: dffffc0000000000 > FS: 00007f21b9d8e700(0000) GS:ffff8881f7000000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 0000001b2d621000 CR3: 00000001c8c46004 CR4: 00000000007606f0 > DR0: 0000000020000140 DR1: 0000000000000000 DR2: 0000000000000000 > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600 > PKRU: 55555554 > Call Trace: > reclaim_pages+0x499/0x800 mm/vmscan.c:2188 > madvise_cold_or_pageout_pte_range+0x58a/0x710 mm/madvise.c:453 > walk_pmd_range mm/pagewalk.c:53 [inline] > walk_pud_range mm/pagewalk.c:112 [inline] > walk_p4d_range mm/pagewalk.c:139 [inline] > walk_pgd_range mm/pagewalk.c:166 [inline] > __walk_page_range+0x45a/0xc20 mm/pagewalk.c:261 > walk_page_range+0x179/0x310 mm/pagewalk.c:349 > madvise_pageout_page_range mm/madvise.c:506 [inline] > madvise_pageout+0x1f0/0x330 mm/madvise.c:542 > madvise_vma mm/madvise.c:931 [inline] > __do_sys_madvise+0x7d2/0x1600 mm/madvise.c:1113 > do_syscall_64+0x9f/0x4c0 arch/x86/entry/common.c:290 > entry_SYSCALL_64_after_hwframe+0x49/0xbe > > madvise_pageout access the specified range of the vma and isolate > them, then run shrink_page_list to reclaim the memory. But It also > isolate the unevictable page to reclaim. Hence, we can catch the > cases in shrink_page_list. > > We can fix it by preventing unevictable page from isolating. > Another way to fix the issue by removing the condition of > BUG_ON(PageUnevictable(page)) in shrink_page_list. I think it > is better to use the latter. Because We has taken the unevictable > page and skip it into account in shrink_page_list. The justification is indeed not clear. This is essentially the same kind of bug as a58f2cef26e1 ("mm/vmscan.c: fix trying to reclaim unevictable LRU page") which has been fixed by checking PageUnevictable before adding it to the list of pages to reclaim. Removing a long existing BUG_ON begs for a much better explanation. shrink_page_list is not a trivial piece of code but I _suspect_ that removing it should be ok for mapped pages at least (try_to_unmap) but I am not so sure how unmapped unevictable pages are handled from top of my head. Please also ad Fixes: $sha > Signed-off-by: zhong jiang > --- > mm/vmscan.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/vmscan.c b/mm/vmscan.c > index f7d1301..1c6e959 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -1524,7 +1524,7 @@ static unsigned long shrink_page_list(struct list_head *page_list, > unlock_page(page); > keep: > list_add(&page->lru, &ret_pages); > - VM_BUG_ON_PAGE(PageLRU(page) || PageUnevictable(page), page); > + VM_BUG_ON_PAGE(PageLRU(page), page); > } > > pgactivate = stat->nr_activate[0] + stat->nr_activate[1]; > -- > 1.7.12.4 > -- Michal Hocko SUSE Labs